Photo voltaic cell



Feb. 9, 1943. c. w. HANSELL PHOTO VOLTAIC CELL,

Filed 095:. 12, 1959 SEMI CONDUCT/VF c m D M R W R W M TRANSPARENT CONDUCT/V5 FILM Inventor Wild/mm Clarence (Ittomeg between the film and menus Feb. 9, 1943 amour micro yon-rare can.

Clarence W. Hanacll, Port Jefferso or to Radio Corporation of tion of Delaware N. Y., assignoa. a corpora- Applioation December 12, 1939, Serial No. 308,830

8 Claims.

This invention relates to a new and useful photo voltaic ce An object of the invention is to provide a new and improved dry type of photo voltaic cell which can convert a larger amount of light energy into direct current electrical energy and which can deliver the direct current energy to external circuits with greater power efficiency.

A feature of this invention is the arrangement and division of the-cell into smaller areas by the interposition of a narrow conducting line or lines across the surface of the cell. Photo voltalc cell elements of the kind to which this invention may be applied, consisttypically of a semi-conductive layer, such as cuprous oxide, deposited on the surface of a metallic disc and coated by a transparent or semi-transparent electrically conducting film. An insulating protective coat is then applied over the entire surface with the exception of a narrow band near the edge where a metallic ring is sprayed. This ring serves as the negative terminal while the untreated side of the disc forms the positive terminal.

A typical cell may consist of a copper disc (or a disc of some other metal which is coated on one side with copper) over which has been placed, by evaporation in vacuum, a layer of silver a few thousandths centimeters thick. The combination is then heated to about 1050 degrees centigrade in the presence of oxygen, after which the disc is cooled and then coated, by evaporation in vacuum, with a very thin layer of metallic silver, gold or platinum. This final layer is thin enough to pass light but thick enough to form an; electrically conducting layer. It is usually overlaid with a thicker layer of conducting material around the outer edge and this thicker layer serves as one terminal of the cell. The metal backing plate is the other terminal.

It has been found that the transparent, elecfilm which connects the active contact surface with the thicker outer ring terminal layer presents a diflicult problem.

The film must be extremely thin in order to let a maximum value of light reach the function the semi-conducting material. On the other hand, an extremely thin film has a high electrical resistance and as such causes a loss of a large part of the electrical energy produced by the cell. Current generated by the photo voltaic effect near the center of the cell must be carried a relatively great distance through thenlm in order to reach the through the center of disc i.

as gold or platinic chloride by heating,

negative terminal. Resistance in the pathwill lower the value of electrical output power obtainable and the voltage at which it is delivered to the external circuit, thus limiting the output and sensitivity of the cell. Also, the resistance of the film limits the cell area which it is practical to use and therefore limits power eificiency, the size and useful rating of individual cells.

By my invention, 1 make it possible to obtain a more eiiicient and sensitive cell and a cell of larger power output rating, by using larger and thinner -films without introducing large effective series resistance. I accomplish this by dividing thecell up into smaller parts of surface area by interposing a network or pattern of narrow conducting lines across the active surface area of the cell.

This invention will best be understood by referring to the accompa. ying drawing, in which:

Fig. 1 is a front elevation of a disc-shaped photo-electric cell; i

Fig. 2 is a cross-section of Fig. 1;

Fig. 3 is a front elevation of a rectilinear type of cell; and

Fig. 4 is across-section of Fig. 3.

Referring now in detail to the drawing, a metallic disc i, which may be copper, has disposed thereon a semi-conductive oxide layer 2 over which is coated a transparent conducting film I, such as previously described. An insulating and protective coat l of transparent lacquer is then applied over the surface 3. A narrow peripheral band 5 of a conducting layer is placed over him 3, preferably band 5 is in the form of a thin metallic'ring. The ring may be provided by evaporation in vacuum, or by electroplating, or by reducing a layer of salts of a metal such or by metal spraying, coating with a colloidal graphite. This ring serves as one terminal of the cell, the other terminal being untreated surface of the metallic disc I. Connected with the metallic ring I is a plurality of long narrow conducting lines 8 which form a conductive path from one portion of the ring to another as it passes interposed between lines 8 are a plurality of intermediate narrow lines I, but shorter in length than lines 8, so that they do not pass through the center of the cell and block out the light rays. Conducting lines it and 1 are formed in the same manner as the metallic band 5 mentioned above.

The modification shown in Figs. 3 and 4 is generally similar to that of Figs. 1 and 2, except that the disc is rectilinear in shape and is bordered by a conducting border U having long narrow conducting lines connecting from one portion of the border to another.

By this invention, it will be seen that instead of applying a good conductive coating only in the form or a ring around the outside periphery, that the narrow line or strips run across the lana of the cell and connect with the main terminal. and that there is in effect obtained a number 01' equivalent smaller cells. each of higher electrical eiilciency, and therefore the lefliciency or the whole cell will be greatly increased. Also, it desired, the whole cell may be made much larger in area in order to obtain a greater output from a single unit without sacrificing eiliciency.

Although only two simple forms of this invention are shown, it is to be distinctly understood that it is capable of taking other shapes and that the lines need not necessarily be straight, but may be of any other suitable pattern to obtain high electrical ei'ilciency.

It will also be understood that although my invention is described as applicable to photovoltaic cells. these same cells may be employed as combination photovoltaic and photosensitive cells. That is. the cells not only produce electrical potential and current when light falls upon them but also exhibit a change in resistance from one terminal to the other when the incident light changes. By applying polarizing potentials from an external source to the cells, the light may be made to control more electrical energy at higher. potentials than ii the photovoltaic eifect alone is used. In particular, ii a polarizing current is passed through the cells in a reverse direction to the direction of flow due to the photovoltaic eiiect, a relatively large electrical potential and power variation may be controlled by the incident light.

What is claimed is:

l. A photo electric cell comprising a disc-like metallic suriace, a semi-conductive layer deposited on said metallic surface, a transparent conductive layer covering said semi-conductive layer. an insulating iilm covering said transparent conductive layer, a conductive iiim coated over and located at the periphery of said cell and in electrical conductivity with said transparent conducthe layer. and a plurality or narrow conductive lines coated over and extending radially from one portion oi said conductive path to another and electrically connected therewith to divide the active surtacearea or said cell into a plurality of smaller parts to decrease its resistance path.

2. A photo electric cell comprising a disc-like metallic surface, a semi-conductive layer deposited on said metallic surface. a transparent conductive layer covering said semi-conductive layer. a conductive film coated over and located at the periphery of said cell, a plurality oi conductive lines coated over and extending through the center of said disc to electrically connect portions oi said conductive path, a plurality of short conductive lines interposed between said narrow connecting lines extending radially on the surface oi said disc. and an insulating iilm covering said transparent conductive layer and narrow conducting lines.

3. A photo electric cell comprising a circular conductive base plate having a light sensitive surface thereon, a transparent conductive layer having a high electrical resistance over said light sensitive surface and inelectrical contacttherewith over. its entire area, a conductive ring around the periphery 0! said transparent conductive laver and in electrical contact therewith. a plurality oi narrow conductive lines extending diametrally across said conductive layer and connected thereto and to said ring, a plurality of conductive lines extending radially inwardly from said ring towards but not to the center of said layer and connected to said layer, and a transparent insulating film covering the area of said layer within said ring.

CLARENCE W. HANSELL. 

